The monstrance had been presented to St Bridget's Church in Killester in 1927. It has not been recovered.

Mosley, 24, with addresses at Cromcastle Park and Gracefield Avenue in Artane, pleaded guilty at Dublin Circuit Criminal Court to burglary at the church on June 13 last year.

He further pleaded guilty to the robbery of a mobile phone at Harmonstown Dart Station on 27 June 2015.

Mosley also pleaded guilty to burglary at a house at Glenwood Road, Edenmore on January 13 this year and to making a threat towards Sergeant Basil Grimes in the Criminal Courts of Justice two days later.

One of the men handed over his mobile phone and Mosley ran off. He was later recognised from CCTV and arrested.

He told gardai he “didn't really remember” much about the night as he had been abusing alcohol and drugs.

Garda Eoin Kennedy told the court that Mosley went to a house in Edenmore, where he claimed to know the brother of a teenager living there. The teenager let him into the porch of the house but Mosley, who appeared agitated, went upstairs looking for the teenager's brother's bedroom.

He grabbed an ornamental sword which was in the bedroom and when the teenager told him it was blunt, Mosley said: “I'll still be able to stab you with it.”

Mosley then picked up an iPad but left it back as he couldn't unlock it. He then fled on a stolen bike - but left his phone charging in the bedroom.

Gda Kennedy said the defendant claimed the teenager's brother owed him money, but this was not the case.

While in court on January 15 for a bail hearing in relation to the house burglary, Mosley made threatening gestures to Sergeant Basil Grimes by making the shape of a gun with his hand and pointing it to his head.

Gda Kennedy said: “He mouthed the word 'Boom' while staring at Sergeant Grimes. He then said 'Bang, bang, bang, I'm going to put a bullet in your brain and I am going to take you away from your kids.'”

Defence counsel Pieter Le Vert said Mosley, who has two young children, wished to apologise to the garda and his victims.

Mr Le Vert said Mosley made the threat to the sergeant in the wake of an unsuccessful bail hearing.